Recombinant DNA technology offers new ways to study genetic eye disease. One important use is in the mapping of the diseases on the human genome. We are in the preliminary stages of finding a linkage marker for ARRP (Autosomal recessive retinitis pigmentosa). Approximately 500 different family pedigrees from the National Registry of the National Retinitis Pigmentosa Foundation have been examined to identify the best families suitable for a linkage study. The most important criteria are: pedigrees that are clearly autosomal recessive and with a large number of affected siblings or with a large number of siblings (affected plus unaffected). It appears that a sufficient number of suitable families exist that linkage could be detected at a recombination fraction of 0.2 or less. A number of DNA probes have been collected that detect highly polymorphic variations in human DNA.